Given the way the Sterling / Euro exchange rate has been changing in recent weeks, Koni FSDs can only get even more expensive. The Euro costs about 86p at the moment. A year ago it was about 72p. That's a rise of over 19%. I thinks it takes about 3 hours labour to fit 4, if that helps.
I live in sheffield so I know exactly what you mean about our roads, more like a massive off road course really ! lol, anyway I had a quote from sarah at awesome Gti for FSD's a few weeks ago and fitted inc alignment was £612.44 including VAT.